1. Field of the Invention
The invention relates to an imaging method for medical examinations which includes the following steps:
acquiring a set of measurement values at measuring points distributed in the frequency domain, PA1 weighting the measurement values in dependence on the density of the measuring points, PA1 generating an image in the space domain by applying a Fourier transformation to the weighted measurement values of the set.
2. Description of Related Art
ISMRM 1996, page 359, discloses a method of this kind for the field of MR examinations (MR=Magnetic Resonance). According to the known method, the weighted measurement values are first convoluted with a gridding kernel so as to enable a Fast Fourier Transformation (FFT) to be carried out. After the FFT, the resultant values must be divided by the Fourier transform of the gridding kernel so as to obtain a perfect image.
In the case of a method in which the measuring points are not equidistantly distributed in the frequency domain, it is necessary to weight the measurement values in dependence on the density of the measuring points (the lower the density, the higher the weight with which a measuring point is taken into account). In the case of such irregular distributions the customary definition of the density as a number of measuring points per space interval does not make sense, because this measure fluctuates as a function of the magnitude of the space interval and an infinitely small space interval cannot be suitably considered. According to the known method, the measuring points are situated on a spiral, or on a plurality of spiral arms, and the density for a measuring point is defined as the content of the surface area enclosed by the perpendicular bisectors to the connecting lines to the preceding and the next measuring points with neighbouring spiral arms. This method is not suitable for sequences of the EPI type or other MR sequences involving a very irregular distribution of the measuring points. During MR examinations such an irregular distribution may also occur due to eddy currents or non-ideal gradient amplifiers or due to the use of methods involving asymmetrical echos.